Escaping the recent past: which stimulus dimensions influence proactive interference?

Proactive interference occurs when information from the past disrupts current processing and is a major source of confusion and errors in short-term memory (STM; Wickens, Born, & Allen, Journal of Verbal Learning and Verbal Behavior, 2:440-445, 1963). The present investigation examines potential boundary conditions for interference, testing the hypothesis that potential competitors must be similar along task-relevant dimensions to influence proactive interference effects. We manipulated both the type of task being completed (Experiments 1, 2, and 3) and dimensions of similarity irrelevant to the current task (Experiments 4 and 5) to determine how the recent presentation of a probe item would affect the speed with which participants could reject that item. Experiments 1, 2, and 3 contrasted STM judgments, which require temporal information, with semantic and perceptual judgments, for which temporal information is irrelevant. In Experiments 4 and 5, task-irrelevant information (perceptual similarity) was manipulated within the recent probes task. We found that interference from past items affected STM task performance but did not affect performance in semantic or perceptual judgment tasks. Conversely, similarity along a nominally irrelevant perceptual dimension did not affect the magnitude of interference in STM tasks. Results are consistent with the view that items in STM are represented by noisy codes consisting of multiple dimensions and that interference occurs when items are similar to each other and, thus, compete along the dimensions relevant to target selection.

Validation of prognostic models among patients with advanced heart failure.

BACKGROUND: The ability to accurately predict heart failure outcomes is essential to guiding treatment decisions but several competing risk stratification models exist. METHODS AND RESULTS: We prospectively collected data on 280 patients with advanced heart failure recruited from 16 sites across the United States. Deaths and cardiac transplantations within the following 4 years were identified. Medline was searched to systematically identify widely cited heart failure severity classification models predicting long-term survival among patients with heart failure, and 4 were selected for validation. We used Kaplan-Meier survival curves, receiver-operating characteristic curves, and Cox proportional hazards modeling to identify the prognostic significance of each model's risk score and the individual contribution of the clinical components within each model. Average follow-up was 31.2 months; 148 deaths or transplantations occurred. Each model that we evaluated identified patients with significantly different prognoses. However, each was limited in overall predictive power, and many component patient characteristics did not have independent prognostic significance. Prognostic factors found to be most powerful within their models included: increasing age, ischemic cardiomyopathy, history of cardiomyopathy, ankle edema, decreased peak oxygen consumption, and absence of beta-blocker use. CONCLUSION: Although each of the models succeeded in risk-stratifying patients to some extent, all 4 models had shortcomings. There is a need for a contemporary model, derived from a patient population managed in accordance with current heart failure guidelines, applicable to all heart failure etiologies, relying on readily available clinical data.

A randomized, 48-week, placebo-controlled trial of intensive lifestyle modification and/or metformin therapy in overweight women with polycystic ovary syndrome: a pilot study.

OBJECTIVE: To obtain data from a pilot randomized trial on the effect of metformin therapy and lifestyle modification on ovulation and androgen concentrations in women with polycystic ovary syndrome (PCOS). DESIGN: Prospective, randomized, placebo-controlled pilot trial. SETTING: Academic medical center. PATIENT(S): Thirty-eight overweight or obese women with PCOS. INTERVENTION(S): All subjects were randomized to one of four 48-week interventions: metformin 850 mg two times per day, lifestyle modification plus metformin 850 mg two times per day, lifestyle modification plus placebo, or placebo alone. MAIN OUTCOME MEASURE(S): Recruitment, dropout, and compliance with a long-term lifestyle intervention in PCOS; preliminary estimates of treatment effect on ovulation, as measured by weekly urinary pregnanediol glucuronide, and on total T and free androgen index. RESULT(S): It was necessary to screen seven women to have one subject randomized. The dropout rate was 39%, with the majority of dropouts occurring within the first 24 weeks. Mean body mass index was >39 mg/kg(2). Modest weight reduction was found in all treatment groups, with the most significant reduction occurring with the combination of metformin and lifestyle intervention. Significant androgen reduction occurred in the combination group only. Ovulation rates did not differ significantly between groups. However, when data were analyzed by presence or absence of weight reduction in subjects, independent of treatment group, the estimated odds ratio for weight loss was 9.0 (95% confidence interval 1.2-64.7) with respect to regular ovulation. If weight loss occurred during metformin therapy, the odds ratio for regular ovulation was 16.2 (95% confidence interval 4.4-60.2). CONCLUSION(S): Key methodologic issues for a large-scale, randomized trial of lifestyle intervention in PCOS include minimizing early dropout from the lifestyle intervention and including a range of body mass index that is not skewed toward severe obesity. Weight reduction might play the most significant role in restoration of ovulation in obese women with PCOS.

Hypocaloric jejunal feeding is better than total parenteral nutrition in acute pancreatitis: results of a randomized comparative study.

OBJECTIVES: The aims of this study were to define the indications for, and to evaluate the cost-effectiveness of, nutritional support in patients with acute pancreatitis. METHODS: All admissions during the 12-month period from January through December 2000, were entered into a common management protocol consisting of an initial 48-h fast with i.v. fluids and analgesics. After 48 h, those patients who were improving were restarted on oral feeding (group O). The remaining patients were randomized to receive nasojejunal (group EN) or parenteral feeding (group TPN). The randomization study was continued until 50 patients had been accrued. Outcomes in the three groups were compared with respect to length of hospital stay, duration of feeding, complications, and hospital costs. RESULTS: A total of 156 admissions were evaluated in the first 12 months. Of these, 87% patients had mild disease, 10% moderate, and 3% severe; 62% were related to alcohol abuse, 18% gallstones, and 8% idiosyncratic drug reactions. Of the patients, 75% improved on 48 h bowel rest and i.v. fluids, and were discharged within 4 days. The remainder were randomized to jejunal elemental (n = 26) or parenteral (n = 27) feeding. Duration of feeding was shorter with EN (6.7 vs 10.8 days, p < 0.05) and nutrition costs were lower, representing an average cost saving of $2362.00 per patient fed. EN was less effective in meeting estimated nutritional requirements (54 vs 88%, p < 0.0001), but metabolic (p < 0.003) and septic complications (p = 0.01) were lower. Subgroup analysis of patients with severe disease showed similar findings. CONCLUSION: Despite concerns that metabolic expenditure is increased and that food-stimulated pancreatic secretion might exacerbate the disease process, hypocaloric enteral feeding seems to be safer and less expensive than parenteral feeding and bowel rest in patients with acute pancreatitis.